It is currently common practice in military track-laying vehicles to arbitrarily suppress operator commanded engine speeds at low transmission ratios where heavy load operating conditions are likely to occur. This is done to prevent the higher levels of heat rejected by the heavily loaded vehicle power system (internal combustion engine and transmission) from exceeding the capacity of the cooling system to adequately dissipate the heat and thus maintain safe operating temperatures. By suppressing commanded engine speed, engine power is reduced, thereby limiting the heat rejected by the power system to safe levels within the capacity of the cooling system to dissipate.
It will be appreciated that the degree of arbitrary suppression of commanded speed must be predicated on the worst possible operating conditions, which of course don't always exist. Thus, vehicle performance is often prejudiced when it is unnecessary to do so. For example, in cold weather, cooling capacity is enhanced to the point where engine speed commands could be executed to the fullest or at least to a greater extent than the arbitrary set degree of suppression without overheating the power system. Also, the vehicle power system load may be less than that anticipated in establishing the arbitrary degree of command suppression. It will be appreciated that it would be highly desirable to continuously afford military vehicles the most optimum operating performance possible, consistent with the capability of the cooling system to maintain the operating temperatures of the power system within safe limits.
It is accordingly an object of the present invention to provide an improved engine speed control system.
A further object is to provide a control system of the above-character, wherein optimum vehicle performance is achieved consistent with the maintenance of safe operating conditions.
Another object is to provide a control system of the above-character, wherein engine speed commands are suppressed only when cooling system capacity is exceeded.
An additional object is to provide a control system of the above-character, wherein engine speed commands are modified in varying degrees of suppression to bring the heat rejected by the power system to a safe level sustainable by the cooling system.
Yet another object is to provide a control system of the above-character, wherein the degree of speed command suppression is adjustable up or down in accordance with power system rejected heat so as to afford the most optimum vehicle performance possible under any given operating conditions.
Other objects of the invention will in part be obvious and in part appear hereinafter.